جستجوی مقالات مرتبط با کلیدواژه « net primary production » در نشریات گروه « کشاورزی »

Carbon sequestration is the ability of plant biomass and the soil to absorb atmospheric carbon dioxide and store it for a long time. Therefore, carbon sequestration occurs when the rate of absorption of carbon dioxide by plants from the atmosphere, is larger than the total soil respiration rate, plant respiration and plant biomass cut (Anderson et al., 2008). Today, agriculture is effective in carbon sequestration through as an important factor in in order to mitigate the effects of climate change. In the past, carbon sequesters are mainly raised in relation to forests. But today, crops production or animal husbandry can also be effective by maintaining plant residues and proper consumption of organic fertilizers obtained in soil in carbon sequestration (Seyedi, 2016). Therefore, this study was conducted in order to evaluation the carbon sequestration potential in canola plant tissues in agroecosystems Sorkhankalateh region, Gorgan county.

This study was conducted to evaluation the carbon sequestration potential in above- ground and below ground tissues of canola (Brassica napus L.) in agricultural lands of Sorkhankalateh region (Gorgan County) during 2021-2022. In this study, 50 canola fields were selected and sampling from the fields based on the W pattern in the four geographical directions of the region. An electric burn furnace method was used to determine the conversion coefficients of carbon sequestration potential in above- ground and below ground tissues (including siliques, seeds, stems, leaves and roots). As well as, the ratio of above- ground to below ground tissues and harvest index were estimated to determine the net primary production based on carbon content in the above ground tissue, below ground and total plant, and the carbon allocation coefficients in each of the canola plant organs. Finally, using the ArcGIS software version 10.3, the amount of carbon sequestration potential in each of the canola organs was presented in the form of a map, and all the data used were analyzed using SAS software version 9.3.Results and DiscussionBased on the findings of this study, the average deposited carbon in total plant tissues in under cultivated fields of Hayola 50 cultivar was equal to 6657.47 kg per hectare and in under cultivated fields of Trapper cultivar equal to 6560.33 kg per hectare. So that the average carbon sequestration potential was obtained in the stem in two Hayola 50 and Trapper cultivars equal to 2012.36 and 1993.97, in seed 1717.20 and 1639.95, in pod 1676.77 and 1608.36, in leaf 602.90 and 615.72, and in root 648.21 and 703.30 kg per hectare, respectively. Also, the shares amount of the allocation coefficient of each of the economic tissues, stem, leaf and silique, root and root secretions were obtained, in two Hayola 50 and Trapper cultivars equal to 21.17 and 20.42, 63.60 and 63.49, 9.22 and 9.74, and 5.99 and 6.33 percent, respectively. In this study, the average total carbon sequestation potential in above- ground and below ground tissues was equal to 6610.86 kg per hectare. The highest and lowest carbon sequestation potential was obtained for stem with 2081.35 kg per hectare and leaf with 759.89 kg per hectare, respectively. Also, in the survey of carbon sequestration in above- ground and below ground tissues in canola fields, it was determined that there was a significant difference in 99% level. The results of carbon sequestration maps showed that there was the highest carbon sequestration rate in the fields located in the west and northwest, and carbon sequestration rate was lower in the fields located in the southern and eastern regions.

Spatiotemporal changes of net primary production (NPP) is one of the essential indicators in determining rangeland ecosystem condition. Therefore, the aim of current research was to map and monitor the actual and potential NPP of rangeland ecosystems in Kohgiluyeh and Boyer-Ahmad province, using CASA and Miami models, MODIS and field data from 2009 to 2018. The accuracy of the produced NPP maps was assessed in 253 sampling sites located in different vegetation types with good, fair and poor rangeland conditions, using linear regression. Results showed that the difference between actual and potential NPP was greater than 56 gr C/m2/month, which can be a sign of human impacts and interferences in the rangeland ecosystems of the region. The highest and lowest relationships between modeled and field productions were observed in the Astragalus spp. - Bromus tomentellus vegetation type with good rangeland condition (R2=0.84) and Astragalus sieberi- Stipa capensis vegetation type with poor rangeland condition (R2=28), respectively. The present research findings indicated the importance of drought conditions, vegetation type and rangeland condition in estimating the actual and potential NPP and the difference of these productions can be used as an index to determine and monitor the condition of rangeland ecosystems.

Vegetation changes can change the rainfall and temperature cycle and also climate fluctuations, especially temperature and precipitation parameters, have significant effects on vegetation. Climate change causes restriction for plant activities which cause changes in vegetation indices including NPP. Considering that Qazvin plain has been affected by climate fluctuations and drought in recent years, in this study, the relationship between NPP and temperature, standard deviation of temperature, precipitation and standard deviation of precipitation was investigated in this plain. Annual NPP was gained using MODIS satellite imagery for 2001-2020 and using meteorological data, the average annual temperature, total annual rainfall and standard deviation of these two parameters were calculated for each year. Then using linear regression analysis in TerrSet, the relationship between NPP and meteorological parameters was determined. The results showed that the most important factor affecting NPP was related to the temperature and its standard deviation, when they are entered into the equation simultaneously which was effective in 48.8% of the area. The least effective variable was related to the entry of the precipitation and its standard deviation into the equation, which was effective in only 0.4% of the region. Due to the seasonal precipitation, it can be concluded that the standard deviation is not very effective on NPP. Among the land uses in the region, the sensitivity of NPP to temperature, precipitation and their standard deviation in agricultural lands was more than other land uses.

Primary production is an important component in the biological cycle in terms of carbon storage and a key indicator for evaluating of ecosystem function. In this study, net primary production and its components were investigated in the coastal zone of Iranian basin of Caspian Sea during four seasons from 2018 to 2019. In addition, the effective environmental factors on spatial-temporal distributions of net primary production have been studied. As a results, mean (±SD) of Chl-a, euphotic depth (Zeu), active photosynthetic radiation (PAR), maximum primary production per unit of Chl-a (PBopt) and daily net primary production (DNPP) were obtained 2.54±3.23 mg/m3, 28.9±6.8m, 40.42±16.84 Einstein/m2.day, 5.05±1.11 mgC/mgChl-a.h and 2.04±0.73 gC/m2.day. The value of DNPP in the central region was more than the western and eastern regions. It probably is due to effects of wind and waves turbulent on re-suspension of sediment and decrease of light penetration in water column in the western and eastern regions. The seasonal variation of net primary production was in order: autumn>summer>spring> winter. The significant higher NPP in autumn than other seasons (p< 0.05, ANOVA-test), primarily caused by Chl-a and PBoptic. Based on regression and PCA tests, temporal-spatial changes of DNPP has been significantly affected by the two variables of Chl-a and PBoptic.  In general, the classification of trophic state based on net primary production showed that 52% of the data had trophic states in the range of oligo-mesotroph  and mesotroph (49%) to eutroph (3%) and 48% of the data were in the oligotroph group (mainly in the eastern region).

In this study, land degradation in Isfahan province in the period of 2001 - 2014 was monitored using trends analysis in terms of two indices of NDVI and RUE. To do this, MODIS satellite images with MOD13A2 code was used to investigate the vegetation degradation and for calculating the RUE, which is obtained from the NPP to rainfall ratio. The MODIS images with MOD17A3 code was used to calculate NPP and Kriging method was applied for obtaining rainfall map. The results showed that NDVI had an increasing trend while RUE had a decreasing trend based on annual rainfall. Evaluation of land degradation in the time period (2001-2014) and comparing the regression relationship between the two indices of NDVI and RUE in different land uses (agriculture, rangeland, forest and desert) of the study area showed that RUE trend was increasing in agriculture, rangeland and forest land uses, so that in 2001, the value of this index in the mentioned land uses was 0.2, 0.142 and 0.149, respectively and 0.61, 0.099 and 0.106 in 2014. In the desert regions, the trend of the two indices was decreasing, so that the value of RUE in 2001 and 2010 was decreased by the factor of 0.097 and 0.2131 g c m2 per year, respectively. Based on the results, it can be seen that the ecosystem of the study area is degrading.

IntroductionThe imbalance between anthropogenic emissions of CO2 and the sequestration of CO2 from the atmosphere by ecosystems has led to an increase in the average concentration of this greenhouse gas (GHG) in the atmosphere. Enhancing carbon sequestration in soil is an important issue to reduce net flux of carbon dioxide to the atmosphere. Soil organic carbon content is obtained from the difference between carbon input resulting from plant biomass and carbon losses the soil through different ways including soil respiration. CO2 emission varies largely during the year and is considerably affected by management type. The goal of this investigation was to study the effects of application of manure and chemical fertilizer on CO2 flux and carbon balance in agricultural system.
Materials and MethodsIn order to evaluate the carbon dynamics and effect of fertilizer and manure management on soil respiration and carbon budget for winter wheat, an experiment was conducted as a randomized complete block design with three replications in research field of Faculty of Agriculture of Ferdowsi University of Mashhad for two years of 2010-2011 and 2011-2012 . The experimental treatments were 150 and 250 kg chemical nitrogen (N1 and N2), manure (M), manure plus chemical nitrogen (F-M) and control (C). CO2 emission was measured six times during growth season and to minimize daily temperature variation error, the measurement was performed between 8 to 11 am. Chambers length and diameter were 50 cm and 30 cm respectively and their edges were held down 3 cm in soil in time of sampling so that no plant live mass was present in the chamber. Carbon budgets were estimated for two years using an ecological technique.
Results and DiscussionThe net primary production (NPP) was significantly higher in the F2 and F-M treatments with 6467 and 6294kg ha-1 in the first year and 6260 and 6410 kg ha-1 in the second year, respectively. The highest shoot to root ratio was obtained in F2 and the lowest was observed in control plot with 5.1 and 5.2 for first and second years, respectively. The trend of CO2 flux as 250, 220, 200, 170, 160 and 155 mg C m-2 h-1 was gained in the F-M, M, F2, F1 and root-excluded plots, respectively. In general, manure treatments had the highest heterotrophic respiration. The highest of annual soil respiration and heterotrophic respiration were also in M-F treatment with 3257 and 1150 kgC ha-1 for the first year and 3310, 1250 kgC ha-1 in second year, respectively. The annual NPP was 5000 and 5000 kgC ha-1 year-1 for M-F, 5077 and 5100 kgC ha-1 year-1 in F1 and 2065 and 1865 kgC ha-1 year-1 for the control treatment in 2010 and 2011, respectively. The range of annual net biome production (NBP) in the fertilizer and control treatments ranged from -400 to -150 kg C ha-1 year-1, suggesting the loss of carbon in the field. On the other hand, NBP in the M was 1400 and 1200 kgC ha-1 year-1 in 2010 and 2011, respectively and the M-F was 1300 and 1100 kgC ha-1 year-1 in 2010 and 2011, respectively.
ConclusionThe results of this experiment showed that in the wheat ecosystem, the carbon emission is higher than the carbon entry into the soil. The results also indicated that manure application in agro-ecosystems is a necessary approach to mitigate carbon losses in the winter wheat ecosystem and the results indicated a high correlation (> 0.9) between soil temperature and CO2 flux which was positive and exponential. Soil respiration increased under the influence of fertilizer treatments (both chemical fertilizer and manure) but, the main reason for the increased soil respiration under application of chemical fertilizers was autotrophic respiration. While both respiration of autotrophic and heterotrophic increased in manure treatment.

Nowadays, temperature increase, rainfall decrease and its effect on the time dynamics of carbon fixation cycle still are faced by many uncertainties. Net Primary Production (NPP) is one of the main factors of carbon cycle; precipitation and temperature measurement are known as two useful tools to study different ecosystems stability and resilience in terms of climate. Hence, in this study, NPP distribution affected by climate parameters of temperature and precipitation have been investigated in four ecosystems of forests, grassland, irrigated agriculture and rain fed agriculture during the period of 2003-2010. Considering climate conditions of biomes, NPP estimation at regional scale was done based on the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) MOD17 NPP product. The results showed that the regression relation was weak between NPP and rainfall for four studied ecosystems, in the other words, low coefficient between these two variables has caused no justified relationship between them. The regression relation between temperature and NPP in forests, pastures and rain-fed agriculture ecosystems follows quadratic equations with determined coefficient over 0.55. The results of this study show that the forest ecosystem resilience to water and temperature tensions is more than other ecosystems, and irrigated agriculture has the least resilience.